ISO 27145-4:2016

Overview

ISO 27145-4:2016 specifies the communication requirements for connecting vehicle on-board diagnostics (VOBD) systems with external test equipment under the World‑Wide Harmonized On‑Board Diagnostics (WWH‑OBD) GTR. The standard defines how to successfully establish, maintain and terminate diagnostic communication, enabling plug‑and‑play access to vehicle diagnostic information. It is intended as the single, worldwide communication standard for VOBD access and covers OSI layer requirements across physical, data link, network, transport, session, presentation and application layers.

Key technical topics and requirements

• Supported data links: diagnostic communication over Controller Area Network (DoCAN, ISO 15765‑4) and over Internet Protocol (DoIP, ISO 13400 series). The concept allows future extension to additional media.
• OSI layer mapping: specifies layer‑by‑layer services and references (transport: ISO 15765‑2 / ISO 13400‑2; data link: ISO 11898‑1, ISO 15765‑4, IEEE 802.3; physical: ISO 11898‑2, ISO 13400‑3).
• Initialization and network scenarios: procedures for initialization sequences and network setup for both DoCAN and DoIP.
• Transport, session and presentation layer details: mapping of data‑link independent service primitives to DoCAN/DoIP, PDU mappings (T_PDU → N_PDU/DoIP_PDU), timing parameters and session handling.
• Logical addressing and timing: external test equipment and ECU logical addresses, diagnostic protocol timing constraints and maximum number of WWH‑OBD servers/ECUs.
• Diagnostic connector and physical requirements: physical interface descriptions and rules for wired connections.
• Operational constraint: support of only one WWH‑OBD‑compliant external test equipment communicating with a vehicle at a time.
• Scope note: use cases deriving from country‑specific implementations of GTR No. 5 are excluded.

Practical applications and who uses this standard

ISO 27145-4 is essential for:

• OEM vehicle communication architects designing compliant diagnostic interfaces.
• Aftermarket diagnostic tool vendors and test equipment manufacturers implementing plug‑and‑play DoCAN/DoIP connectivity.
• Tier‑1 suppliers and ECU software engineers integrating diagnostic servers and logical addressing.
• Regulatory compliance teams and test laboratories performing WWH‑OBD validation and conformity testing.
• Automotive network engineers implementing transport/session mappings and timing behavior.

Applications include OBD compliance testing, development of diagnostic tool stacks (DoCAN/DoIP), vehicle integration testing, and harmonizing diagnostic access across international markets.

Related standards

• ISO 27145 series (Parts 1, 2, 3, 6)
• ISO 14229‑1 / ISO 14229‑2 (UDS diagnostic services)
• ISO 15765‑2 / ISO 15765‑4 (DoCAN)
• ISO 13400 (DoIP)
• ISO 11898‑1 / ISO 11898‑2 (CAN physical/data link)
• IEEE 802.3 (Ethernet)
• SAE digital annexes (J1930‑DA, J1979‑DA, J2012‑DA, J1939)